Southern African leaders last night said Zimbabwe's politicians must form a power-sharing government immediately and end a deadlock over ministeries, but their call was rejected by Morgan Tsvangirai.

South Africa's president, Kgalema Motlanthe, called on leaders to "show political maturity" in resolving a dispute over cabinet seats following the deal signed in September, which saw Robert Mugabe stay president and Tsvangirai, who won contested elections prior to the unopposed re-election of Mugabe, appointed prime minister. Tsvangirai has refused to take his post as long as Mugabe controls all key ministries, including those for security and for finance.

The emergency summit of the 15-state Southern African Development Community (Sadc), in Johannesburg, is the highest-level intervention to date.

Last night Sadc called for Tsvangirai's Movement for Democratic Change party to co-manage Zimbabwe's disputed home affairs ministry with the ruling Zanu-PF.

Tsvangirai said he was "shocked and saddened" by the outcome of the summit, after more than 12 hours of talks on the impasse and on violence in east Congo.

"We need to form an inclusive government, today or tomorrow," Sadc executive secretary Tomaz Salamao said last night. "Sadc was asked to rule and took a decision, and that's the position of Sadc. Now it's up to the parties to implement."

Zimbabwe's state-run press said Mugabe would not give up key ministries. Justice minister Patrick Chinamasa said that the government had agreed to share control of the interior ministry, which runs the police: "The ball's in Tsvangirai's court."